This application claims the priority of 198 27 628.1, filed Jun. 20, 1998, the disclosures of which is expressly incorporated by reference herein.
The invention relates to a fuel injection valve for internal combustion engines, and more particularly, a fuel injection valve having a nozzle needle longitudinally and displaceably guided in a nozzle body. A tensioning nut axially braces the nozzle body with a nozzle holder. optionally, by way of a transition piece whose respective faces rest on an adjacent face, the fuel injection valve may also have at least one feed pipe extending in the nozzle body and the nozzle holder, having fuel-carrying transfer points between the nozzle holder and the nozzle body.
It is known that fuel injection valves used in high-pressure injection systems suffer from leakages at the interface between the nozzle body and the nozzle holder. This is because, depending on the injection system, fuel is intermittently or continuously subjected to high pressure in this area.
To avoid leakage risks, a fuel injection valve is known from German Patent Document DE 196 08 575 A1, in which an intermediate disk is clamped in between the nozzle body and the nozzle holder. The intermediate disk sealingly rests in a special manner by means of faces on the axial faces of the nozzle body and the nozzle holder. For increasing the sealing effect of the intermediate disk, which is required particularly in the case of injection valves with very high injection pressures, one of the interacting faces on the nozzle body and on the intermediate disk is constructed to be arched toward the outside in a crowned manner. This construction provides a uniform distribution of force at the sealing cross-section on the intermediate disk and on the nozzle body.
In high-pressure injection systems, particularly common rail systems, prestressing force is increased for ensuring tightness. However, this prestressing force may result in a deformation of the nozzle body, whereby the close play between the nozzle needle and the nozzle body is no longer ensured. This would result in friction and wear.
It is an object of the present invention to reliably seal off by special measures at the fuel injection valve, the connection between the nozzle body and the nozzle holder, without increasing prestressing forces. The measures taken should also be suitable for systems which are subjected to particularly high pressures, for example, common rail injection systems.
As the result of the measures according to the invention, by means of a raised contact surface having surface parts, a targeted relief of all surfaces on one of the interacting faces is achieved which are not absolutely necessary for the sealing. Thus the surfaces are at least reduced to the endangered fuel transfer points.
The raised contact surface may be provided with another surface part which, as an additional support point, offers a secure hold of the mutually braced housing parts of the fuel injection valve.
In this case, it is particularly advantageous for a surface part to extend on the outside diameter of the face, which results in an optimal supporting and sealing function which is preferably suitable for injection systems which are operated with high fuel pressures.